1. Field of the Invention
The present invention relates to a resist coating and developing unit for forming a resist film on a substrate, developing a substrate that has been exposed, and forming a desired pattern on the developed substrate.
2. Description of the Related Art
In a fabrication process for a semiconductor device, the photolithography process is used. In the photolithography process, resist solution is coated on a substrate such as a semiconductor wafer. With a photo-mask, the resist film is exposed. The exposed resist film is developed. Thus, a resist mask having a desired pattern is formed on the substrate.
The photolithography process is performed by a system of which a coating and developing unit 1A and an exposing unit 1B are connected as shown in FIG. 13. When a semiconductor wafer (hereinafter referred to as wafer) is processed, the coating and developing unit 1A comprises a loading and unloading portion 11, a transferring arm 12, a coating and developing portion 13, and an interface portion 14. The loading and unloading portion 11 loads and unloads a wafer carrier C to/from the coating and developing unit 1A. The transferring arm 12 removes a wafer from the carrier C placed at the loading and unloading portion 11. The coating and developing unit 1A is connected to the exposing unit 1B. When a wafer W is transferred to the coating and developing portion 13 through the transferring arm 12, the coating and developing portion 13 forms a resist film on the wafer W. The resultant wafer W is transferred to the exposing unit 1B. The exposing unit 1B exposes the resist film. Thereafter, the resultant wafer W is returned to the coating and developing portion 13. The coating and developing portion 13 develops the resist film on the wafer W. The resultant wafer W is returned to the carrier C.
After the processed wafer W has been accommodated to the carrier C, the operator or automatic transferring robot transfers the carrier C from the loading and unloading portion 11 to an inspecting unit 15. The inspecting unit 15 inspects the line width of the resist pattern formed on the wafer W, the overlap of the resist pattern and base pattern, coating irregularity of resist, developing defect, and so forth. When the inspected result of the wafer W is acceptable, the wafer W is transferred to the next process. When the inspected result of the wafer W is unacceptable, the wafer W is transferred to a cleaning unit 16. Since a plurality of devices are formed as a plurality of layers on the wafer W, the wafer W is loaded and unloaded to/from the coating and developing system several ten times. Thus, the cleaning unit 16 uses a plurality of kinds of chemicals corresponding to the processes. The wafer W is immersed with a relevant solution. Thus, the resist is dissolved and removed. Consequently, the wafer W is regenerated to the pre-state of the coating and developing processes. Thereafter, the wafer W is transferred to the coating and developing system. In the coating and developing system, the same processes are performed.
In the coating and developing unit, a monitor wafer is used besides a product wafer. After a resist film is formed on the monitor wafer, the monitor wafer is transferred from the loading and unloading portion 11 to the inspecting unit 15. The inspecting unit 15 inspects the film thickness of the resist film on the monitor wafer so as to adjust the number of rotations of a spin chuck of the resist solution coating unit. After the film thickness of the monitor wafer has been inspected, the monitor wafer is transferred to the cleaning unit 16. The cleaning unit 16 dissolves and removes the resist film on the monitor wafer. Thus, the monitor wafer is recycled.
However, since a carrier C is transferred from the conventional coating and developing system to the inspecting unit 15 and wafers W accommodated in the carrier C are removed and inspected one by one in the inspecting unit 15. Thus, the throughput of the system is low. In addition, when the resist coating unit is adjusted with a monitor wafer, it is transferred from the coating and developing system to the inspecting unit. After the film thickness of the resist film of the monitor wafer is inspected, the resist film is manually cleaned and removed and then the resultant wafer is returned to the coating and developing system. Thus, the operator should walk between the coating and developing system and the external inspecting unit. In addition, the operator should manually clean the monitor wafer. Thus, in the conventional system, the operator should perform troublesome operations. Moreover, it is difficult to automatically perform such operations.